This invention relates to a method for extracting ingredients of oil-containing seeds. More particularly, this invention relates to a method of treating oil-containing seeds for extraction of cell substances, especially protein, of oil-containing seeds under the condition in which enzymes, especially oxidizing enzymes, are deactivated by heating characterized by triturating oil-containing seeds which have not been soaked in water, in deoxygenated hot water or deoxygenated hot water containing metal ion chelating agents, etc. under the anaerobic condition.
An object of this invention is to provide a method of treating oil-containing seeds whereby an aqueous dispersion of cell substances of the oil-containing seeds (hereinafter called "milk" in contrast with the term "residue" or "cake") is obtained with higher protein content, reduces viscosity and diminished unpleasant odor (inclusive of bean smelling and grassy smelling).
A further object of this invention is to provide a method of treating oil-containing seeds for extracting cell substances thereof which is simple in operation and economically advantageous.
Various methods have hitherto been proposed to obtain seed milk with reduced unpleasant odor (bean smelling and/or grassy smelling) at high extraction rate from oil-containing seeds. One of those methods substantially comprises soaking oil-containing seeds (or microorganisms) in an aqueous solution containing a metal ion chelating agent and/or a reducing agent for saturation, thereafter heating to 70.degree. C. or higher, and triturating the seeds (or microorganisms) for extraction. Although this method is very excellent, it is still disadvantageous in that grassy smelling is, although slightly, produced by the action of lypoxydase, a long soaking time is required and thus a large scale facilities are necessary when the soaking is continuously carried out, and a large amount of waste water must be treated. As an improvement of this method, a method comprising directly triturating uncrushed seeds soybeans for instance, which have not been soaked in water, in hot water in the presence of oxygen under the aerobic condition in order to deactivate oxidizing enzymes. However, in this method, extraction of protein is only 63% as seen in the comparative data shown hereinafter, and extraction of the bean milk is at low level.
It is already known that the percentage of protein extraction is increased by treating soaked and triturated soybeans or pulverized defatted soybeans with an alkali solution at room temperature. But a method in which uncrushed soybeans which have not been soaked in water for saturation is directly triturated in hot diluted alkali solution so as to obtain bean milk containing coagulative protein, which can be used as the raw material for production of bean curd, is not yet known.
We have made an extensive study in search of a method in which the above-mentioned disadvantages are eliminated. And we have found that: When oil-containing seeds, which have not been soaked in water, are triturated under the anaerobic condition, protein is extracted at higher extraction rate, and bean milk the peroxide value (POV) of which is very low is obtained; and when the trituration is carried out with hot aqueous solution containing a metal ion chelating agent, etc. under the anaerobic condition, bean milk the POV and viscosity of which are further lower is obtained, and thus the extraction rate of protein is further increased. This invention is based on this finding of ours.